Specification is ongoing in 3rd Generation Partnership Project (3GPP) for home nodes in the Wideband Code Division Multiple Access/Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (WCDMA/UTRAN) and in the Evolved Universal Terrestrial Radio Access Network (EUTRAN). In a EUTRAN environment, the home node may be referred to as a home E-UTRAN NodeB (HeNB). In a UTRAN environment, the home node may be referred to as a home NodeB (HNB). The home node may include a home base station that would provide coverage for the end users and would be connected to the core network using some kind of Internet Protocol (IP)-based transmission. The radio coverage provided is called a femto cell. One of the main drivers for this type of local access is to provide cheaper call or transaction rates/charges when connected via the home node versus other nodes (e.g., eNodeB or NodeB).
The home node would, in most cases, utilize the end user's already existing broadband connection (e.g., cable, any DSL based method denoted as x Digital Subscriber Line (xDSL) family of technologies where Asymmetric Digital Subscriber Line (ADSL) is currently the most common one) to achieve connectivity to the operator's mobile core network and possibly to other nodes (e.g., eNodeB, NodeB, home node). Current 3GPP discussions include possibilities to perform access control in a network having femto cells. For example, discussions address the case when neither the user equipment (UE) nor the core network is allowed to be modified (i.e., how to support legacy pre-Release 8 UEs that do not support the closed subscriber group (CSG) concept). In the System Architecture Evolution/Long Term Evolution SAE/LTE 3GPP Rel-8 standards, a concept known as a CSG has been introduced. With the CSG, particular HeNBs can be associated with certain UEs, where only these associated UEs are allowed to access certain HeNBs. It will be appreciated that the CSG is actually associated with a group of subscribers rather than UEs, but for purposes of discussion, the term UE will often be used as the entity of which the CSG is formed. The allowed CSG Identities (CGS-IDs) are stored in the UE in a CSG White List. Each HeNB broadcasts, in system information, both a CSG indicator and the CSG-ID allocated to it. In this way, the UE can determine, by reading the CSG-ID from the system information and comparing this to the content of the CSG White List, whether it is allowed to access a particular HeNB. The allowed CSGs for the UE are also stored in the core network so that the core network can perform an ultimate access control (e.g., in case the UE has an outdated CSG White List or misbehaves (e.g., a hacked UE)). This variant of access control is called core network-based access control.
Current discussion also include a radio access network (RAN)-based access control (e.g., in the WCDMA/UTRAN) to support legacy UEs (i.e., UEs without CSG support). In one implementation, the RAN may include an access control database (ACDB). The ACDB may store information regarding the HNBs and which UEs are allowed to access the femto cell or CSG cell provided by each HNB.
While the utilization of the CSG White List appears promising, the transfer of the CSG White list to the UEs is still open in the current discussions. Further, solutions for maintaining the ACDB have still yet to be specified and remain unresolved.